It has been known for about 30 years that poly(aryl ethers), poly(aryl thioethers) and simple aryl sulfones have high thermal stability. For example, it has been known that diphenyl sulfone can be heated to about 470.degree. C. before noticeable decomposition occurs. Also, it has been known that di-p-tolyl sulfone can be distilled at 430.degree. C. without decomposition. These observations have suggested that poly(aryl sulfones) will also have high thermal stability. Accordingly, there has been considerable effort expended in the art to prepare polymers of this type.
Prior workers have shown that the preparation of poly(aryl sulfones) is not an easy task. Several approaches have been taken by prior workers to overcome this problem.
One prior art approach is to use a sulfone which has two aromatic rings, and two halogens (one on each ring) as a monomer. This type of reactant is copolymerized with a disodium salt of a dihydric phenol. An example of this type of polymerization is the reaction of 4,4'-dichlorodiphenyl sulfone with the disodium salt of Bisphenol A. As known in the art, the Bisphenol A salt can be substituted with salts of other dihydric phenols.
A problem with this type of reaction is the restriction to use of dihalodiarylsulfones as reactants. Furthermore, use of this type of reactant results in a copolymer having both the desired sulfonyl groups and less desired ether groups bridging aromatic rings. A third problem is that the reaction requires a comonomer amount of the aromatic dihalide.
Polysulfones have also been made by reacting aromatic sulfonyl halides using Friedel-Crafts catalysts, as in U.S. Pat. No. 3,951,918 infra. Friedel-Crafts catalysts are moisture sensitive, and corrosive. For these reasons use of such catalysts also presents problems to be overcome.
A third prior art approach to preparing aromatic polysulfones is the use of an activated aromatic dihalide and an aromatic disodium disulfinate as reactants. Such a reaction is suggested by Sato et al in their 1982 publication cited below. A problem with this approach is the need of an activated co-reactant, such as bis(4-chloro-3-nitrophenyl) sulfone. This approach also uses co-monomer amounts of each reactant, and requires use of a tetraalkylammonium salt as a catalyst.
A fourth approach suggested in the art is the preparation of a polysulfide, followed by oxidation to a polyarylsulfone. This type of process is set forth in the United States Technical Disclosure cited below. As can be seen by referring to the reference, this approach has been suggested for preparation of aromatic block copolymers. A problem with this approach is that it is not straightforward, since it requires two reactive steps and two product isolations. It also requires co-monomer amounts of reactants. The oxidation is conducted in the presence of glacial acetic acid, which can be corrosive if water is present. Also, poly(phenylene sulfide) is highly insoluble and difficult to contact with the oxidant in order to get complete reaction. Furthermore, peroxide oxidants used in this procedure must be correctly stored and used to prevent problems from occurring.
This invention solves the prior art problems noted above. It does not require two reactant materials present in about nearly equal molar amounts. It can prepare products which are devoid of oxygen linkages. It does not use a Friedel-Crafts catalyst or an onium catalyst, and it does not require two reaction steps or an oxidant.
Thus, by means of this invention there is provided a convenient, one-step synthesis of poly(aryl sulfones) which does not require a catalyst that is difficult to use or handle. Furthermore, by means of this invention there is provided for the first time a process for the self-condensation of a haloaryl sulfinate salt. Also, there is provided for the first time an initiator for starting the self-condensation of such salts. Stated another way, this invention comprises the discovery of initiation properties in certain, known types of compounds. It comprises (i) a self-condensation, and (ii) an aromatic nucleophilic substitution.